The Young Writers Society is a website for writers aged between 13 and 25. It has a forum and a very nice blog, all geared to assist young writers hone their craft:

By promoting creative writing as a past time, the site seeks to encourage creative thinking, proper grammar, and better writing.

Today, the Young Writers Society is proud to boast well over 3,000 members, over 10,000 poems and stories, and a review to story/poem ratio of nearly 6 to 1. The average age on the site is 17.5, and the site receives over 400 posts per day on average. There is no other site for young writers on the web that even comes close.

Great stuff!